Background Human leukocyte antigen B27 (HLA-B27)-associated uveitis is the most common reason for non-infectious uveitis. This purpose of the research was to study the expression and significance of T lymphocyte subsets and CD4+ CD25+ T regulatory (Treg) cells in peripheral blood of patients with Human leukocyte antigen B27-positive acute anterior uveitis (HLA-B27-positive AAU). Methods The concentrations of Th1, Th2, Th17, CD4+ CD25+, and CD4+CD25+FOXP3+ Treg cells in peripheral blood were tested by flow cytometry. C-reactive protein (CRP) in peripheral blood was detected by immunoturbidimetry (ITM). Spearman's rank correlation was used to analyze the relationships between the concentration of Th1, Th2, Th17, CD4+ CD25+, and CD(4)(+)CD(25)(+)FOXP3(+) Treg cells in peripheral blood and disease activity score and CRP content. Results The ratio of both gamma [interferon (IFN)-gamma] (+)CD4(+) Th1 cells and CD4+IL-(17+)Th17 cells in peripheral blood of patients with HLA-B27-positive AAU (P=0.041) was higher than that of the control group (P=0.002). The concentration of CD4(+)CD25(+)FOXP3(+) Tcells in peripheral blood of patients with AAU was lower than that of the control group (P=0.026). The concentration of Th1 cells in peripheral blood of the patients had no correlation with disease activity score (P=0.50) or CRP content (P= 0.383). This was also true of the concentration of Th2 cells (Disease activity score: R=0.068, P=0.817; CRP content: R=0.439, P=0.116). Th17 cell concentration positively correlated with disease activity score (R=0.805, P=0.001). The concentration of CD4(+)CD25(+) T cells showed no correlation with disease activity score (R=-0.209, P=0.472) or CRP content (R=-0.169, P=0.563), whereas the concentration of CD4(+)CD25(+)FOXP3(+) T cells negatively correlated with disease activity score but did not correlate with CRP (R=-0.248, P=0.392). Conclusions The peripheral blood of patients with HLA-B27-positive AAU showed a higher expression of interferon-gamma and interleukin-17 cel l s in CD4(+) T cells, whereas CD4(+)CD25(+)FOXP3(+) T cells displayed a lower expression of the cytokines. The balance between Th17 cells and CD4+CD25+FOXP3+ T cells may contribute to the activity of HLA-B27-positive AAU.